A deck is a big outdoor investment, and our climate works against it — UV in summer, water and freeze-thaw in winter. A little routine maintenance keeps it safe and good-looking for decades. Below we answer the five upkeep questions Ontario homeowners ask most. This page is part of our complete guide to building a deck in Ontario.

Stain, sealing and cleaning

Why is my stain peeling, and how often should I re-stain?

Stain usually peels because it was a film-forming product, or it went on a damp, dirty, or brand-new (still-wet) board. Re-coat a penetrating semi-transparent stain every 2–3 years, sooner on sun-baked south faces. Let new pressure-treated lumber dry for weeks to months first, clean the deck, and stain only when the wood is genuinely dry.

Penetrating stains soak in and wear away gradually, so they never peel the way a film does — that’s why they’re the safer choice in Ontario. The board you started with matters too: if you’re weighing wood against a no-stain option, our composite vs wood decking guide lays out the real maintenance trade-off.

How do I clean greying, mouldy or slippery boards?

Clean greying, mould, or slippery film with a deck cleaner or an oxygen-bleach (sodium percarbonate) solution and a stiff brush, working with the grain, then rinse well. Avoid harsh chlorine bleach and high-pressure washing that furs the wood. For composite, use the manufacturer’s recommended cleaner. Greying is just UV — clean and re-stain wood to restore it.

Winter: snow, salt and ice

Should I shovel snow, and can I use salt or ice-melt?

Shovel with a plastic blade (not metal), pushing parallel to the boards to avoid gouging. Skip rock salt — it corrodes fasteners and damages wood and some composites. If you need traction, use a deck-safe ice melter (calcium magnesium acetate) or plain sand. Don’t pile snow against the house, where it traps moisture at the ledger.

You don’t have to clear every snowfall — a normal deck is built to carry snow load. Clear paths for safe footing, keep snow off the ledger area, and avoid the metal shovel and rock salt that quietly wreck fasteners and the ledger connection over a few winters.

Spring inspection and septic clearances

Spring inspection — what do I look for?

Each spring, walk the deck looking for what fails over winter: a loose or rusting ledger, heaved footings, soft or rotten wood, popped fasteners, wobbly guards, and loose handrails. Push and pull on the railings. Fix the structural items first — especially anything at the ledger or the guard — before the deck gets heavy use.

• Ledger & flashing — firm, no rust streaks, no gap opening at the house.
• Footings — level, no winter heave lifting posts off their bases.
• Guards & handrails — solid when you push and pull; gaps still under 100 mm.
• Boards & fasteners — no soft, rotten, or cupped boards; no popped screws or nails.

Most of these are details from elsewhere in the guide — the ledger and the guard and railing are the two safety-critical ones, so check them first and fix them before anyone leans on a loose rail.

Can I build over or near my septic tank or field?

Generally no. You can’t build a deck — especially one with footings — over a septic tank or the leaching bed. Footings can crush pipes, and the structure blocks access plus the oxygen the field needs. Keep the required clearance from the tank and bed, and check your municipality and septic rules before you dig.

If your build is anywhere near a septic system, sort the clearances before you finalize the deck’s location. Our guide to septic systems in Ontario covers the setbacks, and tank/field access has to stay open for pump-outs and repairs for the life of the system.

Frequently asked questions